Blame the Phoenicians.
The roots of sherry go back three thousand years in Spain, where it appears that the Phoenicians brought vines and the knowledge of wine making. The city of Jerez, a key area for the production of sherry, was established by the Phoenicians as Xera. Other cultures contributed to the development of this wine and it was imported to Rome. When the Moors occupied Spain in the 8th century, despite the Muslim prohibition against the consumption of alcohol, they continued the cultivation of grapes for the production of wine for medicinal purposes and for raisins
Originlate 16th century: alteration of archaic sherris, interpreted as plural, from Spanish (vino de) Xeres or ‘Xeres (wine)’ (Xeres being the former name of Jerez)